DE202015104356U1 - Ionization electrode, use thereof and gas burner with such an ionization electrode - Google Patents

Abstract

Ionization electrode (10) having an elongate, in particular wire-shaped electrode body (11) made of a material resistant to at least 1200 ° C scale and shape, characterized in that the wire-shaped electrode body (11) by a correspondingly elongated or wire-shaped body, in particular stiffening wire (12 ) of the same material to form a "double wire electrode" (13) is stiffened.

Description

The present invention relates to an ionization electrode according to the preamble of claim 1, the use of such an ionization electrode for flame monitoring of a gas burner, as well as a gas burner with a flame monitoring, which comprises an ionization of the type in question here.

Ionization electrodes with a respective elongated, in particular wire-shaped electrode body made of a material resistant to at least 1200 ° C. scale and shape are generally known. These electrodes are used for permanent flame monitoring. It makes use of the knowledge that in the presence of a gas flame, the air gap is ionized. Connected to the ionization is a rectifier effect, which causes a current flow to the electrode in the case of a potential difference between electrode and burner. This current flow is evaluated or processed by an electronic unit and thus serves for flame monitoring, in particular for controlling the gas inflow. In this way, the combustion can be stabilized.

It should also be noted at this point that scaffolding refers to the resistance of a material to scaling, scaling being a corrosion of a metal caused by direct oxidation with oxygen, forming a dense oxide (protection) layer on the material , A good scale resistance is usually due to a high chromium content of steel and can be increased by further additions of aluminum, silicon or the like. In order for electrodes in heating torches to withstand the high temperatures occurring there permanently, they are often formed from a material with a resistance to scale of at least over 1200 ° C., preferably up to 1450 ° C.

• – Ionisationselektrode
• – Flamme
• – Brenner
• – Versorgungsspannung

so, dass ein Ionisationsstrom fließt. Der Ionisationsstrom wird in einer Steuerelektronik selektiert und ohne Aufbereitung als Eingangssignal einer Steuerlogik zugeführt. Die Steuerlogik stellt fest, ob ein Strom fließt oder nicht fließt. Da sich die Ionisationselektrode während des Betriebs dauernd in dem Flammenbereich befindet, muss sie sowohl zunderfest als auch formbeständig sein.Ionization of the aforementioned type, which are generally rod-shaped or wire-shaped, are mounted in the combustion chamber, that they protrude with its tip in the flame area. During operation of the burner, the flame completes the monitoring series connection of

• - Ionization electrode
• - Flame
• - Burner
• - Supply voltage

such that an ionization current flows. The ionization current is selected in a control electronics and fed without processing as input to a control logic. The control logic determines if a current is flowing or not flowing. Since the ionization electrode is constantly in the flame area during operation, it must be both solid and dimensionally stable.

Ionization electrodes of the type mentioned are inter alia from the DE 10 2010 004 345 A1 known. It is about an electrode that can withstand long-term undamaged temperatures of up to 1200 ° C due to the base material used. Moreover, there it is proposed to provide the elongate, in particular rod-shaped or wire-shaped electrode body with an electrode body supplementary part made of a material with a scale resistance of less than 1000 ° C. This is to ensure that a possible signal drop is bridged shortly after the burner start.

The present invention is also concerned with improving the monitoring performance and flexural rigidity of an ionization electrode. It was recognized that the previously available solutions are still subject to heavy wear in terms of the ionization signal. After a prolonged period of operation, the ionization signal weakens, which is crucial for reliable ignition, in particular during the starting process.

In order to increase the bending stiffness of an ionization electrode and also to achieve a larger surface area of the same, which could counteract a signal drop, especially at the burner start, it might be thought to increase the diameter of the rod or wire-shaped electrode. However, such an increase in diameter has several disadvantages. Thus, the material, in particular the ceramic used for an electrode would have to be changed, which would increase the one-off and ongoing production costs. A larger electrode means more material that prolongs the warm-up phase. During the warm-up phase, the ionization signal is correspondingly weaker and can be measured worse.

Furthermore, it has been found that conventional ionization electrodes deform due to gravity at high temperatures in the flame region, which in extreme cases can lead to a short circuit with the burner.

• 1. Das Ionisationssignal ist höher und stabiler gegenüber einer herkömmlichen „Einfachelektrode”. Diese Erkenntnis ist von großer Wichtigkeit, da durch Alterungsprozesse das Ionisationssignal mit steigender Betriebsdauer abnimmt. Ein ausreichendes Ionisationssignal ist jedoch zur eindeutigen Flammenerkennung notwendig.
• 2. Die Biegesteifigkeit der Elektrode wird erhöht. Dies ist insbesondere in dem Bereich wichtig, in dem die Elektrode den höchsten Temperaturen ausgesetzt ist. Durch die Versteifung wird verhindert, dass sich die Elektrode während ihrer Einsatzdauer verformt, insbesondere unter ihrem Eigengewicht, wobei sich die Ionisationselektroden in der Regel jeweils etwa horizontal in die Flammen hineinerstrecken.

According to the invention, the above-mentioned problems or objectives are achieved or achieved in that the wire-shaped electrode body of the ionization electrode is stiffened by a correspondingly elongated or wire-shaped body, in particular stiffening wire of the same material to form a "double-wire electrode". Such a "double wire electrode" has the following advantages:

• 1. The ionization signal is higher and more stable compared to a conventional "single electrode". This finding is of great importance, since the ionization signal decreases with increasing operating time due to aging processes. However, a sufficient ionization signal is necessary for clear flame detection.
• 2. The bending stiffness of the electrode is increased. This is particularly important in the area where the electrode is exposed to the highest temperatures. The stiffening prevents the electrode from deforming during its duration of use, in particular under its own weight, with the ionization electrodes usually extending approximately horizontally into the flames in each case.

It is important that both the electrode itself as well as the associated stiffening wire from the same material are produced, in particular Kanthal A1, APM ^®, Haynes ^® 230W or CrAl 20-5. These are in each case an aluminum- or silicon-containing steel alloy with high scale resistance of more than 1200 ° C.

Since only the electrode wire, but not the stiffening wire are passed through the ceramic, a low-cost standard ceramic can be used without adjustments.

Preferably, the stiffening wire extends approximately parallel to the wire-shaped electrode body and also has the same dimensions as the electrode body, namely diameter and in particular also length.

To increase the dimensional stability and mutual assignment of wire-shaped electrode body on the one hand and stiffening wire on the other hand, the stiffening wire and the wire-shaped electrode body are at least partially firmly connected to each other, in particular welded. Especially suitable for this purpose is a laser welding, which can be carried out very precisely and without deformation.

In a specific embodiment, stiffening wire and the associated wire-shaped electrode body have a length of 20 to 100 mm, in particular about 84 mm, and a diameter of 2.0 to 4.0 mm, in particular of 3.0 mm. With these dimensions, a significantly higher ionization signal is obtained by means of the additional stiffening wire, since the surface of the electrode as a whole is considerably increased by the additional stiffening wire. This is particularly important in the starting phase, in which the main task of the electrode is to detect a flame signal.

At the same time, the flexural rigidity of the electrode as a whole is increased by the second stiffening wire. As stated at the outset, the thermal load at temperatures above 1100 ° C. and the weight of the electrode may lead to a deformation of the electrode, which then causes a short-circuit with the burner. The electrode usually extends approximately horizontally at a distance of about 5 to 20 mm above the burner or the burner surface. With a deformation of the electrode due to its own weight down to the burner, the insufficient short-circuit may lead to the mentioned short circuit. It should be remembered that the burner or the burner associated with the flames with respect to the ionization electrode defines a positive pole (technical current direction). The ionization electrode itself defines a minus pole.

The inventive solution with additional stiffening wire, the flexural rigidity of the electrode is increased by a factor of 5, and thus largely precludes deformation in the direction of the burner.

As also stated above, one could have achieved a surface enlargement by a larger electrode diameter; but then you would not have achieved the last-mentioned considerably greater bending stiffness. The same applies if you had simply extended the electrode wire. A larger diameter of the electrode wire would also have the disadvantage that it takes longer for the wire to reach the operating temperature, which is a hindrance to the ionization signal during the starting phase. In addition, a special ceramic would have to be made to enclose a wire with a larger diameter, which is not desired in terms of manufacturing technology.

As can be seen from the above explanations, the ionization electrode according to the invention is particularly suitable for flame monitoring of a gas burner. For this purpose, it should be used primarily.

• – Ionisationselektrode der erfindungsgemäßen Art,
• – Flamme,
• – Brenner und
• – Versorgungsspannung,

wobei die Ionisationselektrode in die Flamme ragt und einen Ionisationsstrom zur Kennzeichnung des Betriebes des Gasbrenners abgibt, wodurch die Gaszufuhr über ein Ventil einstellbar ist.The invention also relates to a gas burner with a flame monitoring of a series circuit of

• Ionisation electrode of the type according to the invention,
• - Flame,
• - burners and
• - supply voltage,

wherein the ionization electrode projects into the flame and an ionization current for characterizing the Operation of the gas burner gives off, whereby the gas supply is adjustable via a valve.

Hereinafter, a preferred embodiment of an ionization electrode according to the invention and also the arrangement thereof within a gas burner will be explained in more detail with reference to the accompanying drawing. This shows in

1 an embodiment of an inventively designed ionization electrode in a perspective view;

2 a part of the electrode acc. 1 in rear view;

3 a part of the electrode according to the invention in side view;

4 the arrangement of an ionization electrode according to the invention within the arrangement of a gas burner in a schematic representation;
and

5 a part of the arrangement acc. Fig. On an enlarged scale.

In the 1 to 3 is an ionization electrode according to the invention 10 with a so-called "double wire electrode" 13 shown. The "double wire electrode" 13 is defined by an elongated, namely wire-shaped electrode body 11 from an aluminum or silicon-containing steel alloy, in particular from the material Kanthal ^APM® , and a parallel extending and with the electrode body 11 firmly connected stiffening wire 12 of the same material as the wire-shaped electrode body 11 , The material of electrode body 11 and stiffening wire 12 is at least up to 1200 ° C scale and dimensionally stable.

In the illustrated embodiment, the "double wire electrode" includes 13 two deflection or bending areas 20 . 21 , This allows the ionization electrode 10 save space within the gas burner in association with the flames mount. In principle, it is also conceivable that the "double wire electrode" is continuously elongated, ie without deflection or bending areas.

The wire-shaped electrode body 11 extends through a ceramic insulator 22 therethrough. This cylindrically formed in the present case insulating body 22 includes a retaining plate 23 , by means of fixing the ionization electrode 10 takes place at the gas burner housing. At the "double wire electrode" opposite side of the insulator 22 is the wire-shaped electrode body 11 with a plug contact 24 can be coupled via which then the connection to a supply voltage takes place.

The cylindrical insulating body 22 indicates the "double wire electrode" 13 facing an annular gap, which defines a so-called. "Creepage distance". This prevents adhesive residues on the electrode.

The attachment and sealing between insulator 22 and holding plate 23 done by means of press fit and silicone.

Furthermore, it should be noted that the wire-shaped electrode body 11 inside the insulating body 22 is preferably glued rotatably.

The stiffening wire 12 extends only to the insulator, ie stands on this, while the wire-shaped electrode body 11 through the insulating body 22 extends through to be connected to the corresponding supply voltage can.

The connection between the wire-shaped electrode body 11 and stiffening wire 12 takes place accordingly 2 by means of longitudinally spaced apart Schweißabschnnitten. Concrete are in the illustrated embodiment 4 Welding sections provided. These welding sections are each obtained by appropriate laser welding without additional material. Preferably, the welding takes place on both sides of the "double wire electrode" 13 ,

Based on 4 and 5 can be the arrangement of the ionization electrode according to the invention 10 according to the 1 to 3 inside a gas burner 15 detect. The gas burner 15 includes a housing 26 , At the top of the case 26 openings are provided through which fuel gas flow outward and to form flames 16 can ignite. The gas is supplied at the bottom of the housing 26 via a gas supply channel 27 , Within this gas supply channel is a valve 28 arranged, which via a solenoid 29 from a closed to an open position and vice versa and in any intermediate positions between closed and open position is movable, depending on the control logic of an electronic control unit 30 , This controller 30 is via an ignition transformer 31 with a ignition electrode 32 connected. This ignition electrode is arranged opposite to the ionization electrode in the illustrated embodiment.

The ionization electrode 10 used with the "double wire electrode" described above 13 into the flames defines a minus pole. In contrast, that defines the flames 16 associated page of the housing 26 a plus pole. Between these two poles there is a DC voltage of about 20 to 100 V.

The electronic control unit 30 is connected to an AC voltage, here about 230 V.

As stated above, in the presence of a gas flame 16 the air gap or air between burner housing and ionization electrode 10 ionized. In 5 the ion flow is shown schematically.

To the housing 26 migrate negative ions and to the "double wire electrode" 13 wander plus ions. With this ionization and ion migration, a rectifier effect is connected, which causes a current flow to the electrode; and this current flow is from the electronic control unit 30 evaluated and used to control the solenoid 29 and thus the valve 28 recycled. Through the valve 28 will the gas supply 18 regulated.

With the reference number 17 is in 4 generally the "supply voltage" at the ionization electrode in the range of 20 to 100 V marked.

With the reference number 19 are characterized within the gas burner effective gas deflecting elements, in particular sheets, which are well-known measures within a gas burner.

To the ignition transformer 31 it should be mentioned that an ignition voltage in the order of 5 to 25 kV can be generated by this.

to 5 It should also be mentioned again that the plus and minus ions are ions of the air ionized by the flames or their heat and light, which after polarization becomes the "double wire electrode". 13 or to the case 26 hike.

All disclosed in the application documents features are claimed as essential to the invention, as far as they are new individually or in combination over the prior art.

LIST OF REFERENCE NUMBERS

10

ionisation

11

wire-shaped electrode body

12

stiffening wire

13

Double wire electrode

14

welding portions

15

gas burner

16

flame

17

supply voltage

18

gas supply

19

deflecting

20

bend region

21

bend region

22

insulator

23

Retaining plate

24

plug contact

25

circumferential grooves

26

burner

27

Gas supply channel

28

Valve

29

solenoid

30

Electronic control unit

31

Ignition transformer

32

ignition electrode

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010004345 A1 [0005]

Claims (9)

Ionization electrode ( 10 ) with an elongated, in particular wire-shaped electrode body ( 11 ) made of a material resistant to at least 1200 ° C scale and shape, characterized in that the wire-shaped electrode body ( 11 ) by a correspondingly elongated or wire-shaped body, in particular stiffening wire ( 12 ) of the same material to form a "double wire electrode" ( 13 ) is stiffened. Ionization electrode according to claim 1, characterized in that the stiffening wire ( 12 ) approximately parallel to the wire-shaped electrode body ( 11 ). Ionization electrode according to claim 1 or 2, characterized in that the stiffening wire ( 12 ) has approximately the same dimensions, namely diameter and / or length as the wire-shaped electrode body ( 11 ). Ionization electrode according to one of claims 1 to 3, characterized in that the stiffening wire ( 12 ) and the wire-shaped electrode body ( 11 ) at least partially firmly connected to each other, in particular welded. Ionization electrode according to one of claims 1 to 4, characterized in that the stiffening wire ( 12 ) and / or the wire-shaped electrode body ( 11 ) have a length of 20-120 mm, in particular about 84 mm, and a diameter of 2.0 to 4.0 mm, in particular about 3.0 mm. Ionization electrode according to one of claims 1 to 5, characterized in that both the wire-shaped electrode body ( 11 ) as well as the stiffening wire ( 12 ) consist of a steel alloy, in particular Kanthal A1, APM ^® or Haynes 230W ^® . Ionization electrode according to one of claims 1 to 5, characterized in that only the electrode body ( 11 ), but not the stiffening wire ( 12 ) through the insulating body ( 22 ). Use of an ionization electrode ( 10 ) according to one of claims 1 to 6 for flame monitoring of a gas burner ( 15 ). Gas burner ( 15 ) with a flame monitoring of a series connection of - ionization electrode ( 10 ) according to one of claims 1 to 6, - flame ( 16 ), - burners ( 26 ) and - supply voltage ( 17 ), the ionization electrode ( 10 ) with its electrode body ( 11 ) or its "double wire electrode" ( 13 ) into the flame ( 16 ) and an ionization current for characterizing the operation of the gas burner ( 15 ), whereby the gas supply ( 18 ) via a valve ( 28 ) is adjustable.

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